Korea University

About: Korea University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 39756 authors who have published 82424 publications receiving 1860927 citations. The organization is also known as: Bosung College & Bosung Professional College.

Upconversion Nanoparticles: Design, Nanochemistry, and Applications in Theranostics

Abstract: Applications in Theranostics Guanying Chen,*,†,‡ Hailong Qiu,†,‡ Paras N. Prasad,*,‡,§ and Xiaoyuan Chen* †School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China ‡Department of Chemistry and the Institute for Lasers, Photonics, and Biophotonics, University at Buffalo, State University of New York, Buffalo, New York 14260, United States Department of Chemistry, Korea University, Seoul 136-701, Korea Laboratory of Molecular Imaging and Nanomedicine, National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892-2281, United States

International Comparisons of Educational Attainment

Abstract: Many theories of economic growth stress the role of human capital in the form of education, but empirical studies have been hampered by inadequate data. We describe a data set on educational attainment that we have constructed for 129 countries over five-year periods from 1960-1985. We use census/survey information to fill over 40% of the cells, and we use school enrollment figures in a perpetual-inventory framework to fill the remainder. The data refer to male and female attainment of the adult population at four levels: no-schooling. primary. secondary, and higher. We also provide a rough breakdown into incomplete and complete attainment at the three levels of schooling. We then take account of cross-country variations in the durations of schooling at each level to provide figures on total years of attainment.

Atomically thin p–n junctions with van der Waals heterointerfaces

Abstract: In heterostructures of the transition metal dichalcogenides MoS2 and WSe2, atomically thin p–n junctions are created that show gate-tunable rectifying and photovoltaic behaviour mediated by tunnelling-assisted interlayer recombination. Semiconductor p–n junctions are essential building blocks for electronic and optoelectronic devices1,2. In conventional p–n junctions, regions depleted of free charge carriers form on either side of the junction, generating built-in potentials associated with uncompensated dopant atoms. Carrier transport across the junction occurs by diffusion and drift processes influenced by the spatial extent of this depletion region. With the advent of atomically thin van der Waals materials and their heterostructures, it is now possible to realize a p–n junction at the ultimate thickness limit3,4,5,6,7,8,9,10. Van der Waals junctions composed of p- and n-type semiconductors—each just one unit cell thick—are predicted to exhibit completely different charge transport characteristics than bulk heterojunctions10,11,12. Here, we report the characterization of the electronic and optoelectronic properties of atomically thin p–n heterojunctions fabricated using van der Waals assembly of transition-metal dichalcogenides. We observe gate-tunable diode-like current rectification and a photovoltaic response across the p–n interface. We find that the tunnelling-assisted interlayer recombination of the majority carriers is responsible for the tunability of the electronic and optoelectronic processes. Sandwiching an atomic p–n junction between graphene layers enhances the collection of the photoexcited carriers. The atomically scaled van der Waals p–n heterostructures presented here constitute the ultimate functional unit for nanoscale electronic and optoelectronic devices.

Statistical notes for clinical researchers: assessing normal distribution (2) using skewness and kurtosis

Abstract: As discussed in the previous statistical notes, although many statistical methods have been proposed to test normality of data in various ways, there is no current gold standard method. The eyeball test may be useful for medium to large sized (e.g., n > 50) samples, however may not useful for small samples. The formal normality tests including Shapiro-Wilk test and Kolmogorov-Smirnov test may be used from small to medium sized samples (e.g., n < 300), but may be unreliable for large samples. Moreover we may be confused because ‘eyeball test’ and ‘formal normality test’ may show incompatible results for the same data. To resolve the problem, another method of assessing normality using skewness and kurtosis of the distribution may be used, which may be relatively correct in both small samples and large samples. 1) Skewness and kurtosis Skewness is a measure of the asymmetry and kurtosis is a measure of ’peakedness’ of a distribution. Most statistical packages give you values of skewness and kurtosis as well as their standard errors.